大视场高分辨率连续太赫兹波数字全息成像方法研究

Terahertz digital holography is a combination of terahertz technology and digital holography, which can benefit from the best of both approaches. For example, the terahertz wave has some unique propagation features, such as penetration, non-ionization and water sensitivity. On the other hand, digital holography which makes the detection nondestructive and non-scanning can obtain the quantitative amplitude and phase distributions. The imaging resolution and field-of-view of the terahertz digital holography are restricted by the wavelength of terahertz wave, the characteristics of terahertz sources and the finite size of recorded detectors. And the current resolved power of the system cannot meet the requirements of non-invasive observation, three-dimensional measurements and so on..In this proposal, the continuous-wave terahertz digital holography with high resolution and wide field-of-view is investigated. The experimental imaging resolution and field-of-view will be enhanced so that this technique can be used in practical detection. Firstly, we study the terahertz imaging elements and architecture and demonstrate their influence on imaging resolution and field-of-view. Secondly, compressive sense algorithm is used to improve the sampling rate of terahertz holograms. Meanwhile, the electronic stage is employed to conduct the raster scanning so that the field-of-view of the system can be expanded. Finally, two approaches are presented to achieve the experimental resolution enhancement of continuous-wave terahertz digital holography. One is using two-dimensional terahertz grating to capture the high frequency components of the object wave-front and putting the sub-diffraction patterns together to reconstruct the distinct complex amplitude distributions. The other is that the structured light illumination method with grating would be utilized to demodulate the high-resolution information. Moreover, the experimental verification of the resolution improvement will be carried out. The project will and shall provide a high-resolution and wide field-of-view terahertz phase-contrast imaging method with wide potential prospects.

太赫兹数字全息技术能充分利用太赫兹波穿透性、水敏感性、非电离性等特性，可在该波段下无损、非扫描地获取样品定量的振幅和相位分布，是太赫兹科技和数字全息成像方法的结合体。受限于太赫兹波波长、波源特性和探测器参数等因素，现有太赫兹数字全息技术的实际成像分辨率低、视场小，在众多场合无法满足实际应用的需求。.本项目的研究内容为大视场高分辨率连续太赫兹波数字全息成像方法，旨在提高该技术的成像分辨率，同时扩展其视场，使之成为一种高效、实用的太赫兹波探测手段。首先，针对太赫兹波成像元器件和结构展开研究，分析其对分辨率和视场的影响。之后，发展基于压缩感知算法的太赫兹全息图采样分辨率提高技术，同时通过精确位移扫描扩展成像视场。最后，分别通过衍射光栅收集和结构光照明解调获取样品的高频信息，完成实验研究重建样品高分辨率的再现图像。本项目的开展将提供一种极具应用潜力的大视场高分辨率连续太赫兹波相衬成像手段。

太赫兹全息技术能充分利用太赫兹波穿透性、水敏感性、非电离性等特性，可在该波段下无损、全视场地获取样品定量的振幅和相位分布，是太赫兹科技和全息技术的结合体。本项目的研究内容为发展一种可用于多种领域、应用性好、性能稳定、兼具光谱特性的太赫兹全息表征系统和方法，在太赫兹波全息再现算法优化、成像质量增强、分辨率视场提升、矿物样品表征、新型太赫兹器件等方面取得了一些系列研究成果。项目开展了一系列提高太赫兹全息成像质量方法的研究，包括提出了一种太赫兹波大视场高分辨率全息成像方案，采用太赫兹合成全息图外推法获取高分辨率质量的目标成像结果；运用合成扫描技术有效扩展了全息成像视场，实现了兼顾高分辨率同时可自由扩展成像视场的目的，克服了传统成像分辨率与视场不能兼顾的困难，大大提高了该技术的样品适用性和成像鲁棒性。提出了一种面向矿物表征的太赫兹光谱全息探测系统和方法，对炉甘石、蛋白石、胆矾、页岩、白云石、蒙脱石和高岭土等地学矿物样品以及不同类型高分子黏合剂在热解、矿物水状态、吸附等物性特征方面进行了太赫兹全息光谱表征。研究结果建立了太赫兹全息信号与不同温度、孔隙率、含水率、粒径尺寸矿物的内在联系，对矿山形成、地质演变、地下水循环和地幔运动等方面带来指针意义。进一步开展了太赫兹光学调制器件的研究，包括矿物透镜、光子晶体和光栅器件等相关内容，探索了全息表征系统的新型潜在器件应用。本项目的开展可满足材料无损辨识、医学病理诊断、国防监测探测和油矿资源探勘等众多国民经济和社会发展中重点领域里的可视化研究需求，极具发展潜力并有着非常重要的科学意义与实用价值。